Women in their 30s are having babies at the highest rate since the 1960s, providing a rare bright spot in what’s an otherwise stagnating U.S. population.

For women in their early 30s, the birthrate in 2015 was the highest it’s been since 1964, according to a Centers for Disease Control and Prevention report this year. And the rate for women age 35 to 39 was the highest since 1962, when families were larger and births hit near all-time highs in the baby-boom years.

At the same time, the total number of births to women age 30 to 39 has increased in all states except Connecticut, New Hampshire and New Jersey from 2007 to 2015, according to a Stateline analysis of National Center for Health Statistics data.

And births to 30-somethings accounted for the majority of all births in three states — Connecticut, Massachusetts and New Jersey — and Washington, D.C.

Although hardly a baby boomlet, the higher birthrates among older women help offset a decline in births among younger women age 15 to 24. And they suggest that younger women who are putting off parenthood now may embrace it as they get older, finish their education, establish careers, and become more financially secure.

“Fertility is being displaced later and later into the lives of women, especially educated women, and more and more women are educated,” said Herbert Smith, director of the Population Studies Center at the University of Pennsylvania.

If the trend of more women having babies in their 30s continues, it also holds out hope that the nation can partly replenish its workforce — especially if President Donald Trump follows through on his campaign promises to limit immigration.

As the baby-boom generation ages out of the workplace, the U.S. has depended on immigration to keep its population growing and to maintain its workforce amid declining birthrates. Without a steady supply of new immigrants, who have higher fertility rates than native-born women, the nation’s workforce will start shrinking and could drop over the next 20 years, according to a report this month from the Pew Research Center. (The Pew Charitable Trusts funds the center and Stateline).

A shrinking workforce could be part of a “downward spiral” affecting state economies, according to some projections, if states are unable to get people to fill jobs and pay taxes.

Overall fertility rates in the U.S. are at a historic low of 62.5 births per 1,000 women of childbearing age, 15 to 44, despite the high rates for women in their 30s. There were about 4 million births in 2014 and in 2015, still well below a 2007 peak of 4.3 million and an earlier peak in 1991, when about 4.2 million millennials — the generation born between 1981 and 1997 — were born.

Fertility rates for teenagers and women in their early 20s were at historic lows in 2015. And babies born to 25- to 29-year-olds decreased every year between 2008 and 2013, although they increased by 25,000 in 2014 and by 7,000 in 2015.

The spike in births to older women may help temporarily, if immigration falls off under the Trump administration, said Jennifer Dabbs Sciubba, an associate professor of international studies at Rhodes College in Memphis. But postponing childbirth will not add to the population long term because U.S. women are not having enough babies over the course of their lifetimes, she said.

The low overall fertility rate has spread concern that the nation’s population could stagnate without ongoing immigration.

“If we see continued declines in immigration, in the long run we’ll run into the same types of labor shortages other countries have had,” said Mark Mather, an associate vice president at the Population Reference Bureau.

Putting Off Having Children

Some of the drop in childbirths among younger women in the U.S. may be the result of a drop in unauthorized immigration. Since 2007, the number of babies born to unauthorized immigrants in a given year has declined by almost 100,000, a number that likely will continue to drop if immigration enforcement is stepped up.

Despite worries that less immigration would result in a smaller working-age population, some advocates of limiting immigration see that outcome as more desirable.

“America’s problem is not a low working-age population,” said Steven Camarota, research director of the Center for Immigration Studies, which advocates less immigration and endorses President Trump’s promised crackdown. “It’s the number of working-age people who aren’t working.

“Everybody agrees that a lot of blue-collar workers have lost jobs and their wages are dropping. In that context, does it make sense to keep bringing in more immigrants?” he said.

Some population analysts see a generational change among millennials, who they say are not just putting off childbirth but choosing not to do it at all.

Stewart Friedman, author of the 2013 book Baby Bust, surveyed 2012 and 1992 graduates of the Wharton School of the University of Pennsylvania, where he is a professor, and found that many more millennials than Gen Xers were planning not to have children.

He blamed the change partly on career pressures brought on by the aftermath of the Great Recession, forcing delays in marriage and childbirth. “Women are more interested in establishing careers for their own independent financial security and achievement,” Friedman said.

However, the continued increase in rates for women in their 30s suggests that starting families might have been delayed by the economy rather than ruled out entirely.

“As the economy picks up, it could well be that 30-something millennials will finally begin having children after their recession-related delays,” said William Frey, a demographer at the Brookings Institution. “This would continue to prop up later-age fertility rates and contribute to family-related consumerism.”

If millennial women who are now in their 20s have more children later in life, the number of births could keep rising until at least 2024, when the largest group of them turns 35.

Tia Francis, 33, is somewhat typical of women postponing childbirth until their 30s.

Francis said she didn’t feel prepared for children until she was married and settled into a house in a city she loves, Washington, D.C. It took years of preparation and overcoming a high cost of living for her and her husband, Kwesi, also 33, to get a house.

After Kwesi found the right job as a supervisor for the national passenger train service Amtrak and Tia trained as a real estate agent so her work hours would be more flexible, the couple bought a house in an affordable neighborhood. And they had a son, Jeremiah, who is nearing his first birthday.

“I guess it’s really the age that made me think, it’s time to get going,” Francis said. “I want more than one, so at some point you just have to say, ‘OK, I really have to get a move on if I want to do this.’ ”

Stateline is an initiative of The Pew Charitable Trusts that provides daily reporting and analysis on trends in state policy. Since its founding in 1998, Stateline has maintained a commitment to the highest standards of non-partisanship, objectivity, and integrity. Its team of veteran journalists combines original reporting with a roundup of the latest news from sources around the country. Stateline focuses on four topics that are key to state policy: fiscal and economic issues, health care, demographics, and the business of government.

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